1. Field of the Invention
The present invention relates generally to air filtration. More particularly the present invention relates to a method and apparatus for an air filter that renews itself, automatically greatly reducing the time required for replacement.
2. Background Art
Filters for furnaces and air conditioning equipment are typically rigid, framed units (for residential and commercial applications) or in the form of sheets that are stretched between rolls on either side of an air duct (for commercial and industrial applications). Rigid, framed filters are time consuming to replace. As for the sheet-type filters used in commercial and industrial applications, one of the rolls (on one side of the air duct) is drivable. It may use a stepper motor or may be hand-cranked. In the former case, there is significant expense associated with an automatically controlled filter. In the latter, although some manpower is conserved, the filters still need regular attention.
The timing for replacing or renewing filters is important. Dirty filters result in less flow rate of air which translates to less heat exchange in the HVAC equipment. The equipment must run longer to accomplish the intended goal, and air conditioning equipment may freeze up due to inadequate heat exchange.
There is, therefore, a need for a method and apparatus for providing for a self-renewing air filter for HVAC applications. There is a further need for a self-renewing air filter that renews on demand, that is, when it has become sufficiently dirty to restrict air flow.
U.S. Pat. No. 6,843,834 issued Jan. 18, 2005 “Self-Renewing Air Filter”, which is incorporated herein by reference in its entirety, will not work for a constant flow furnace because it uses a ratchet type advancing system that requires that the air flow starts and stops at times. Accordingly, there is a need for a self-renewing air filter which will work in constant flow air filtering equipment.
Gearboxes have been used for decades to transfer power from a source of power to the place where the power has been used. Rotary power can be geared down with a gearbox so a rotary input can be used to transmit power to a slower and more powerful output, or rotary power can be geared up with a gearbox so a rotary input can be used to transmit power to a faster and less powerful output. But there is a need for gearboxes that are more efficient and easier for the user to understand.